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Arbuscular mycorrhizal fungi (AMF) symbiosis has been shown to improve the ability to obtain nutrients and resist adverse environmental conditions. However, there are few studies on the functions of AMF in the absorption and accumulation of boron (B). Moreover, it is still unclear whether the root colonization rates of AMF are limited by B deficiency. In this study, Camellia oleifera seedlings were planted in normal and boron-deficient substrates, and the seedlings were inoculated with Funneliformis mosseae or left uninoculated. The growth and physiological indices of C. oleifera seedlings were determined. The results of this experiment indicate that AMF inoculation increased the plant biomass, B content, B accumulation, and antioxidant enzyme activity in both normal and boron-deficient C. oleifera seedlings. Furthermore, boron deficiency resulted in a decrease in the AMF root colonization efficiency and the inhibition of C. oleifera seedlings’ growth and physiological activity. These findings suggest that AMF inoculation could improve the resistance to B-deficiency stress. Additionally, the colonization efficiency of AMF was adversely affected by B deficiency; thus, AMF play a cooperative role with B in the growth and physiological functions of plants. The results provide a theoretical basis for taking measures to solve B-deficiency stress in C. oleifera and other plants’ cultivation.

In this paper, an adaptive composite anti-disturbance control of heavy haul trains (HHTs) is proposed. First, the mechanical principle and characteristics of couplers are analyzed and the longitudinal multi-particles nonlinear dynamic model of HHTs is established, which can satisfy that the forces of vehicles in different positions are different. Subsequently, a radial basis function network (RBFNN) is employed to approximate the uncertainties of HHTs, and a nonlinear disturbance observer (NDO) is constructed to estimate the approximation error and external disturbances. To indicate and improve the approximation accuracy, a serial-parallel identification model of HHTs is constructed to generate a prediction error, and an adaptive composite anti-disturbance control scheme is developed, where the prediction error and tracking error are employed to update RBFNN weights and an auxiliary variable of NDO. Finally, the feasibility and effectiveness of proposed control scheme are demonstrated through the Lyapunov theory and simulation experiments.

Characteristics of the surface runoff of four vegetation types in the small watershed of Nver Zhai, Wuling Mountain Area, West Hunan were studied. Results indicated that, from June 10, 2015 to September 10, 2016 the precipitation recorded was up to 1971.80 mm, and there occurred 83 rainfalls during the period of investigation. With the increase in the rainfall, the surface runoff gradually increased, among which the Eucommia ulmoides Oliv. plantation showed significantly high runoff. When the rainfall gradually increased to 30 mm, the surface runoff was highest for the sloping farmland. Under an intense rainfall >50 mm, there was a significant augmentation in the surface runoff of the four types of forest lands, indicating that the soil water content began to reach to saturation. Furthermore, the total runoff of the different types of vegetation, the runoff depth and the runoff coefficient were in the order of: E. ulmoides plantation > Pinus massoniana Lamb. forest > Sloping farmland > maple- Cinnamomum camphora (L.) J. Presl. mixed plantation. Additionally, under the same rainfall, there was a reduction in the runoff with an increase in the evaporation, and the total runoff of maple- C. camphora mixed plantation was the lowest. Bangladesh J. Bot. 50(3): 603-611, 2021 (September)

Camellia oleifera is an essential oil woody plant. The development of the camellia industry can relieve the a China’s pressure of importing edible oil. However, there are few studies on the codon usage bias (CUB) in C. oleifera genes. In this study, the codon usage patterns were analyzed by 35,178 reconstructed genes from the C. oleifera transcriptome. The mean GC and GC3 content of all transcripts was 51.14% and 55.43% respectively. A total of 18 optimal codons were identified, 15 of them ending with A or U. Which indicated the use of A/U codons was high frequency. Furthermore, the natural selection and mutational pressure, both influenced CUB in C. oleifera, however the natural selection was the most deciding factor. The nucleotide excretion of C. oleifera genome is rich. C. oleifera prefers A/U ending codons, and nature selection is one of the most important factors affecting CUB. This study will lay a theoretical foundation for the research of molecular evolution and genetic engineering in C. oleifera.

The variable flexibility of a fish body is believed to play a significant role in improving swimming performance. To explore the effect of non-uniform flexibility on the motion performance of fish under biologically relevant conditions, we set up three different flexible distribution modes for a semi-free filament and compared the motion performance of different flexible distribution modes through numerical simulations. The filament is located in the wake of the front flapping foil; it can swing adaptively in the lateral direction according to the flow situation of the surrounding fluid and finally reach a stable position. The results show that the motion state of the filament will alter with a change in the flexibility of the filament, from moving in the vortex street to moving on the side of the vortex street. In the Benard-von Karman (BvK) vortex streets, the drag coefficient of the filament increases as the flexibility of the filament increases, and the value of the drag coefficient is at a minimum when the flexibility of the filament increases linearly along the length of the filament. Further investigation indicates that at 85%–90% of the filament length (starting from the leading edge), the flexibility of the filament begins to increase significantly, and the filament can obtain its best propulsion performance. The results of this work provide new insights into the role of non-uniform flexibility during the process of fish movement and provide a valuable reference for the design of bionic underwater vehicles.

Organic–inorganic hybrid perovskite materials have attracted significant attention due to their intriguing optical and electrical properties. However, it is a challenge to grow a perovskite thin film with controlled crystallinity and large-sized grains by a simple solution process, which is important for highly efficient and stable perovskite solar cells. Herein, a methylamine-assisted secondary grain growth approach is developed for post-annealing of a methyl ammonium lead iodide (MAPbI3) perovskite film in a controlled methylamine (MA0) atmosphere, leading to the formation of a full-coverage and highly oriented perovskite film with large grain sizes up to tens of microns. The resultant perovskite film shows low trap density, strong photoluminescence, and a prolonged decay lifetime. The perovskite photovoltaic device shows an enhanced power conversion efficiency (PCE) of 20.81% with good environmental stability. The method reported here provides a promising and facile route to fabricate high-quality MAPbI3 perovskite films for efficient optoelectronic devices.

Summary In this study, an adaptive output feedback control with prescribed performance is proposed for unknown pure feedback nonlinear systems with external disturbances and unmeasured states. A no...

Sutherlandia frutescens (syn. Lessertia frutescens), an indigenous southern African species, is important for the local and global phytomedicine's industry. As farming of medicinal plants in South Africa is not extensive, wild populations are also used as a source of material to bulk available cultivated yields prior to industrial processing. This may cause inconsistency in the quality of medicinal products derived from this species, inducing discrepancies in the plant’s therapeutic profile. The current study aimed to elucidate the phytochemical variations among S. frutescens plants growing in different geographical localities, especially in areas which have not been studied before. One set of extracts were generated using a 50% acetonitrile and formic acid solution (0.1%) (v/v). By using a targeted metabolomics approach, two major phytochemical groups, sutherlandins and sutherlandiosides were used to display metabolite-based clusters after LC–MS/MS analysis. Plants from different geographical locations grouped into separate chemical lineages. Another set of ethanol and aqueous extracts of pooled leaf materials were screened for their toxicity effect on the hatching rate of zebrafish embryos and mortality of larvae at different concentrations, ranging from 5 to 300 μg ml−1. We also calculated the LC50 values using a zebrafish microplate bioassay and this value was 297.57 μg ml−1 for the water extract. The aqueous extracts were relatively less toxic compared to ethanol extracts (LC50 value of 40.54 μg ml−1). Both the hatching rate and mortality were negatively affected by increasing extract dosages. The highest concentrations, between 200 to 300 μg ml−1, caused acute lethal effects for both extract types. This study adds additional evidence of the cytotoxicity reported by others in this species and will further aid in the domestication of S. frutescens.

A low-complexity adaptive tracking control strategy for a class of pure feedback nonlinear systems is developed in the presence of completely unknown non-affine nonlinearities, prescribed tracking performance constraints, full states constraints, and input saturation constraint. To handle the input saturation nonlinearity and the constrained states without pre-calculating the bound of virtual controllers, a new coordinate transformation approach is presented with an arc-tangent function and an auxiliary first-order dynamics. Subsequently, to deal with the completely unknown non-affine nonlinearities and the problem of prescribed performance, an inverse hyperbolic tangent function and a Nussbaum function are introduced at each step of back-stepping design, which can guarantee the control errors to vary with prescribed performance functions in time and avoid the “explosion of complexity” issue simultaneously. Then, an adaptive controller is derived from the recursive design procedure without the use of any approximators. The semi-globally uniformly ultimate boundedness of all signals in the closed-loop system and the satisfaction of all constraints are rigorously proved through Lyapunov stability analysis. Finally, the simulation studies on a hypersonic flight vehicle system are worked out to demonstrate the effectiveness and the applicability of the investigated approach.

In this paper, an adaptive state-feedback control technique is proposed for a class of unknown pure-feedback systems. A remarkable feature is that not only the problem of full-state constraints and prescribed performance tracking is solved together, but also the design is an approximation-free control scheme for pure-feedback systems with completely unknown nonlinearities. These properties will lead to a difficult task for designing a stable controller. To this end, a novel prescribed performance-barrier Lyapunov function is developed to guarantee that all the state constraints are not violated and the tracking error is preserved within a specified prescribed performance bound at all times, simultaneously. Then, by utilizing the mean value theorem, Nussbaum gain technique, a low-pass filter and a novel bounded estimation approach at each step of back-stepping procedure, a novel adaptive dynamics surface control scheme is developed to remove the difficulties of pure-feedback characteristic, unknown nonlinearities, unknown control direction and “explosion of complexity”, which can guarantee that the proposed design is universal and low-complexity. Moreover, it is proved that all the signals in the closed-loop system are global uniformly bounded. Two simulation studies are worked out to illustrate the performance of the proposed approach.

Background Sutherlandia frutescens is one of the most promising commercialized, indigenous and medicinal plants of South Africa that is used as an immune-booster, and a traditional treatment for cancer. However, few studies report on its toxicology and dosage in vivo. There is still room to better understand its cytotoxicity effects in animal systems. Methods We prepared two extracts, one with 80% (v/v) ethanol, and the other, with water. Both were studied to determine the maximum tolerable concentration when extracts were applied at 0 to 200 μg/ml to a Tuebingen zebrafish embryo line. The development of zebrafish embryos after 24 h post fertilization (hpf) was studied. A concentration range of 5 μg/ml to 50 μg/ml was then chosen to monitor the ontological development of cultured embryos. A liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) method was used to study the differences of the two experimental extracts. Chemical variation between the extracts was illustrated using chemometrics. Results Both extracts led to bleeding and pericardial cyst formation when applied at high concentrations to the zebrafish embryo culture. Chronic teratogenic toxicities, leading to pericardial edema, yolk sac swelling, and other abnormal developmental characteristics, were detected. The aqueous extracts of S. frutescens were less toxic to the larvae than the ethanol extracts, validating preference for aqueous preparations when used in traditional medicine. Chemical differences between the water extracts and alcoholic extracts were analysed using LC-MS/MS. A supervised metabolomics approach, targeting the sutherlandiosides and sutherlandins using orthogonal partial least squares-discriminant analysis (OPLS-DA), illustrated that sutherlandiosides were the main chemical features that can be used to distinguish between the two extracts, despite the extracts being highly similar in their chemical constituents. Conclusion The water extract caused less cytotoxic and abnormal developmental effects compared to the ethanolic extract, and, this is likely due to differences in concentrations of extracted chemicals rather than the chemical profile per se. This study provides more evidence of cytotoxicity effects linked to S. frutescens using the zebrafish embryo bioassay as a study tool. Electronic supplementary material The online version of this article (10.1186/s12906-018-2303-9) contains supplementary material, which is available to authorized users.

In this study, an adaptive anti-disturbance control scheme is investigated for a class of unknown pure feedback switched nonlinear systems subjected to immeasurable states and external disturbances. Radial basis function neural networks (RBFNNs) are employed to identify the switched unknown nonlinearities, and a Butterworth low-pass filter is adopted to remove the algebraic loop problem. Subsequently, a novel switched neural state observer and a novel switched disturbance are presented via the coupled design method to estimate the immeasurable states and compounded disturbances. Then, an improved adaptive control strategy for the studied problem is designed with the help of a filtering method to eliminate the “explosion of complexity” problem, and certain compensating signals are set up to compensate for the filter errors, where switched updated laws are constructed to lessen the conservativeness caused by adoption of a common updated law for all subsystems. By utilizing the Lyapunov stability theorem, the developed control scheme can guarantee that all signals in the closed-loop system are bounded under a class of switching signals with the average dwell time (ADT), while the tracking error can converge to a small neighbourhood of origin. Finally, simulation results are provided to demonstrate the effectiveness of the presented approach.

A novel self-supporting multi-layer magnetorheological elastomer-based (MRE-based) composite with large magnetic field-induced responsiveness has been designed and fabricated. We characterized its morphological properties, evaluated the impact of fabrication conditions on its field-induced responsiveness, investigated attenuation of its field-induced responsiveness under different storage temperatures along with time and analyzed this mechanism from the perspective of rheology. The results showed that the MRE-based composite had homogeneous dispersing of the magnetic fillers and a clear interface between different layers. The field-induced responsiveness of the MRE-based composite could be affected by the fabrication conditions, and it attenuated at different rates when subjected to different storage temperatures along with time; its attenuation period lasted a few days under room temperature while over one month under low temperature (4 °C). The rheological analysis results indicated a long-term cross-linking process over the storage period along with the attenuation of field-induced responsiveness, which might lead to increasing elasticity (indicated by the loss factor tan δ) and rigidity (indicated by the storage modulus G′) of the MRE-based composite along with the storage period. What’s more, emerging feature of Payne effect could be found on MRE-based composite during cyclic shear, which indicated decline of the mechanical properties due to strain-induced inherent friction. On the other hand, the iron fillers in MRE layer could enhance the shear modulus and lead to MR effect (up to 187%) for the whole composite, which benefits to the magnetic field-induced responsiveness, due to the relative strengthen of the MRE layer against the assist layer. This work presents a better understanding on the attenuation of the field-induced responsiveness, which is important for the future application of the MRE-based composite.

Polygonatum cyrtonema Hua, a rhizome‐propagating herb endemic to China, is used in many traditional Chinese medicines and foods. The hilly mountains in western and southern Anhui province is one of its main natural distribution and artificial cultivation areas. We assessed the genetic diversity and structure of P. cyrtonema germplasm resources in Anhui by nine pairs of SSR primers and selected morphological characters. The results showed that the 13 sampled populations of P. cyrtonema possessed normal levels of genetic diversity but could be clustered into three distinct genetic groups. The levels of within‐group genetic diversity was similar among the three groups, but their distribution areas and morphological characters were remarkably different. Group I was confined to the Tianmu (including Jiuhua) Mountains, group II was distributed in the Huangshan Mountains, and group III was restricted to the Dabie Mountains. Furthermore, the leaf length:width ratio significantly differed among groups, and the peduncle length of group I was significantly shorter than that of the other two groups. Levels of genetic differentiation among the three groups was close to that between different species within the genus. Thus, the three genetic groups of P. cyrtonema should be considered as independent units for conservation and breeding management in the Anhui region.

Nature inspired meta-heuristics has turn out to be an intimidating and ordinary field of research in the midst of researchers who are trying to solve complex optimization problems. Monkey algorithm is new addition in the class of swarm intelligence, which is a good option for complex optimization problems. This paper puts forward an improved monkey algorithm with descending factor, whose basic idea is that a descending factor is used in the climbing process of the basic monkey algorithm to ensure the algorithm escape from local optimal solution and find the global optimal solution. The proposed algorithm tests over benchmark functions and results show that it receives better results for the considered problems.

The nutrient estimation is an important basis for water and fertilizer management in the field. In order to achieve crop nutrient content for variable-rate fertilization, a spectrum device based on the Ocean Optics STS-VIS sensor was developed to measure the spectral reflectance at 350-800 nm. The spectral reflectance data could be measured by optical sensor, data transmission module and the controller. The control software was developed with functions such as acquisition parameters, acquisition control and data management. Before the field application, the calibration experiments were conducted. The correlation was analyzed between the developed device and ASD Field Spec Hand Held 2. The result showed that the average correlation coefficient value was 0.94. It was used to detect the chlorophyll and moisture content of potato plant. The SPAD regression model was established and the determinant coefficient R2 was 0.484, moisture content regression model was established and R2 was 0.735. Results showed that the device has a certain ability to predict chlorophyll content and moisture content of potato leaf.

In order to indicate potato crop water content and guide precision irrigation, non-destructive water content detection of potato crop leaves was studied. Firstly, the spectral reflectance of 355 samples was collected by hyperspectral camera and the leaves water content was measured by weighing method. Secondly, the average reflectance of the whole leaves was extracted, and the sensitive wavelengths of leaf water content were screened respectively by correlation analysis (CA) and competitive adaptive reweighted sampling (CARS). The results were as follows: the 15 sensitive wavelengths located in the range of 1400-1450 nm were selected by CA method. While, there were 13 sensitive wavelengths selected by the CARS algorithm including 976.4 nm, 1037.7 nm, 1044.5 nm, 1061.4 nm, 1108.7 nm, 1139 nm, 1357.8 nm, 1380.7 nm, 1397 nm, 1432.8 nm, 1452.3 nm, 1513.6 nm and 1520.0 nm. Finally, after compared the partial least squares regression (PLSR) modeling results of the water content detection based on two group sensitive wavelengths. The CARS-PLSR was elected to detect the water content of potato leaves. The modeling calibration accuracy of CARS-PLSR was 0.9878, and the validation accuracy coefficient was 0.9366. It provides a new theoretical method for detecting water content of potato plant in the field.

The simulation for a variable fertilization machine could help to show the fertilizing result and provide theoretical guidance in reality machine operation. EDEM (Extended distinct element method) which is a general-purpose software for simulating and analyzing particle system is widely used in simulation experiments of fertilizing machines. In order to optimal design of a variable-rate fertilizer machine. This paper uses EDEM to simulate the spread of three kinds of fertilizers which are potassium chloride, potassium sulfate and urea, commonly used in agriculture, by a centrifugal disc type variable-rate fertilizer applicator. After analysis, the variation coefficients of the lateral homogeneity of the three fertilizers are 43.34%, 26.26% and 39.21%, respectively. The result shows that simulation effect of these three fertilizers is not up to standard, and further research is needed to improve the performance of the fertilizer machine.

The performance test and parameter optimization of variable spraying liquid fertilizer machine was conducted in this research for the uniform spraying of foliar fertilizer. A crop protection of high-clearance tractor with a variable sprayer was used in the experiment. According to the parameter design, three factors and three levels of test were performed based on the Box-Behnken center-united experimental design principles. The performance tests were combined with response surface methodology to analyze spray parameters such as machine walking speed, spray flow rate and plot distance test which would influence Droplet distribution uniformity. A mathematical model was established by using Design-Expert 8.0 software, and the model was analyzed to obtain the optimal combination of spray parameters. The optimized spray parameter combination is: machine walking speed is 4.5km/h, the spray flow rate is 375L/hm 2 , and the distance between the plots is 3m. Under this condition, the minimum variation coefficient of droplet distribution is 10.759%, and the relative error is 9.1% compared with the model prediction value of 9.78%. The results of the study can provide operators with reasonable operating conditions when fertilizing.

The water content of potato leaves in different leaf positions was studied using hyperspectral technique in this research. According to leaf position, the leaves were divided into upper, middle and lower 3 groups. The experiment was conducted, in which the fresh leaves were collected and dried, and the reflectance spectra and water content were measured. The relationship between the spectral characteristics of different leaf positions and water content distribution of potato plants was analyzed. It was found that the reflectance and water content of fresh leaves in different positions were different. With the leaf position from top to bottom, the reflectance increased successively (R upper R middle >R lower) in 1403.6-1704.2 nm and the average value of water content increased in turn. After drying, with the leaf position from top to bottom, the spectral reflectance of leaves decreased successively (R upper

In order to solve the problem of reliable information transmission between data centers and data sources, between data sources and between data centers, as well as the "network island" communication problem, a dynamic MPLS VPN method is proposed, the principle and steps of the method are introduced, and how to apply the method to the supporting platform is explained in detail.

The propulsive performance of an oblique school of fish is numerically studied using an immersed boundary technique. The effect of the spacing and wiggling phase on the hydrodynamics of the system is investigated. The hydrodynamics of the system is deeply affected by the spacing between each fish in the school. When the horizontal separation is smaller than the length of the fish body, the downstream fish exhibits a larger thrust coefficient and greater propulsive efficiency than the isolated fish. However, the corresponding values for the upstream fish are smaller. The opposite behavior occurs when the horizontal separation increases beyond the length of fish body. The propulsive performance of the entire oblique school of fish can be substantially enhanced when the separations are optimized.